1. Technical Field
The present invention relates to an image decoding device which decodes a video coded using inter-view prediction and to an image coding device which codes a video using inter-view prediction.
2. Background Art
Optical disks such as DVDs and Blu-ray discs are widely used to distribute moving picture contents including movies. Particularly, as compared to the conventional DVDs accepting standard definition (SD) videos, the Blu-ray discs are capable of accepting high definition (HD) videos with a maximum 1920×1080 resolution and thus storing videos of higher quality. The optical disks have so far stored ordinary two-dimensional (2D) videos, but in recent years, there has been an increasing demand for an optical disk in which three-dimensional (3D) videos are stored without degradation of their high image quality, along with an increase in the number of movie theaters which offer stereoscopic or 3D video display.
The optical disks storing 3D videos are required to have reproduction compatibility with playback devices capable of reproducing only optical disks storing 2D videos (which devices are hereinafter referred to as “2D playback devices”). If the optical disks storing 3D videos are unable to be reproduced in 2D with the 2D playback devices, two kinds of disks, i.e., “the optical disk for 3D video” and “the optical disk for 2D video”, need to be produced for the same contents, which causes an increase in cost. Thus, the optical disks storing 3D videos are required to be reproducible in 2D with the 2D playback devices and reproducible in 2D or 3D with playback devices capable of reproducing 2D videos and 3D videos (which devices are hereinafter referred to as “2D/3D playback devices”).
A method as shown in FIG. 39 is one of the known conventional examples of the playback device and the optical disk storing 3D videos, which are configured for ensuring reproduction compatibility.
An optical disk 1801 stores multiplexed video streams composed of left-eye video streams storing pictures for left eye and right-eye video streams storing pictures for right eye. The left-eye video streams and the right-eye video streams have the same frame rate, and displayed at alternate times. For example, in the case where the frame rate of the respective video streams is 24 frames per second, the left-eye video streams and the right-eye video streams are alternately displayed at 1/48 second intervals. The respective video streams are multiplexed and interleaved, that is, alternately arranged, in the optical disk 1801, in recording units of image information which are one or more GOPs.
In FIG. 39, the left-eye video streams are interleaved as a stream 1802A, a stream 1802B, and a stream 1802C, and the right-eye video streams are interleaved as a stream 1803A, a stream 1803B, and a stream 1803C, in the optical disk 1801. The stream 1802A, the stream 1802B, and the stream 1802C, where the left-eye video streams are arranged, are arranged based on the seek function, the loading rate, or the like of the optical disk 1801 so that when these streams are sequentially reproduced, the reproduction will not be interrupted.
When the optical disk 1801 is put in a 2D playback device 1804, the left-eye video streams, i.e., the stream 1802A, the stream 1802B, and the stream 1802C are reproduced and thus, 2D video is outputted.
On the other hand, when the optical disk 1801 is put in a 3D playback device 1805 capable of reproducing 3D video, or when the optical disk 1801 is put in a 2D/3D playback device and the 3D playback is selected by a user, the left-eye video streams and the right-eye video streams are alternately loaded in units of interleaved blocks. To be specific, the stream 1802A, the stream 1803A, the stream 1802B, the stream 1803B, the stream 1802C, and the stream 1803C are sequentially loaded in this order in a manner that no seek operations are carried out in the drive.
Of the loaded video streams, the left-eye video streams and the right-eye video streams are provided to the left-eye video decoder and the right-eye video decoder, respectively, in each of which the streams provided are then decoded so that pictures for left eye and pictures for right eye are alternately outputted to a television. It may also be possible that the left-eye streams and the right-eye streams are decoded in the same decoder. These outputted images are viewed as stereoscopic videos through 3D glasses 1806 which switch between the right eye shutter and the left eye shutter per 1/48 second.
Such a configuration enables the 2D playback device to reproduce 2D videos and the 3D playback device or the 2D/3D playback device to reproduce 3D videos, from the disk storing 3D videos. The following patent literature 1 discloses a related art of the technique for ensuring the reproduction compatibility of the optical disk storing 3D videos.
The Joint Video Team (JVT) created as a corporative project of ISO/IEC MPEG and ITU-T VCEG completed a revised standard of MPEG-4 AVC/H.264, which is referred to as the Multiview Video Coding (MVC), in July 2008. The MVC is a standard for collectively coding videos from plural views, which performs prediction coding using not only a similarity from one picture to another in a temporal direction but also an inter-view similarity, thereby providing enhanced compression efficiency as compared to independent coding of videos from plural views.
FIG. 40 is a view showing an example of prediction reference with two views. A view referred to as a base view (which may hereinafter be referred to as the first view) is prohibited from referring to another view, being independently decodable and thus highly compatible with the 2D playback device. In addition, the multiplexing scheme of the MVC is now in a process to standardize the supplemental of the MPEG-2 system standard, and its draft has already been issued as seen in the following non-patent literature 1.
The non-patent literature 1 defines a method of MVC packet-multiplexing video streams, a system target decoder which performs a series of operations including loading of packet-multiplexed MVC data, demultiplexing of the data to take out MVC bitstreams, and inputting them to a decoder, and others.
A playback device according to this scheme includes a buffer of a defined size in the system target decoder. As disclosed in the non-patent literature 1, the buffer includes an elementary stream buffer (EB), a multiplexing buffer (MB), and a transport buffer (TB), which are provided in this order from the closest to the farthest from the decoder. In the following description, these buffers will be collectively referred to as a system target decoder (STD) buffer. It is envisaged that the playback device according to the scheme will be able to decode each frame at a predetermined decoding point in time without overflow or underflow of the STD buffer as long as the reproduction device operates at defined data-load timing and data loading rate.